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I'm working on a potting mix for interior plants. And I want it to hold very little water and it should have great aeration and drainage.

I'm looking for a material (organic/inorganic) that is cheap and in the right granulometry to use as at least 60% of my potting mix. I'll provide the nutrients through fertilization if necessary (if it's an inorganic material, for example).

I see that bonsai folks use turface, but that is not so easy to find and when it's sold as "bolsai soil" it's really expensive.

What would be a good option in this case?

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A cheap ingredient that is available at feed stores is chicken grit. What is available near you may vary but common sources are granite, calcium, flint or oyster shell.

It is sold as tiny sharp edged fragments. It goes well with peat based soil mixes that are often acidic as the calcium or oyster based mixes are usually alkaline.

It does not degrade and promotes good drainage.

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It depends on what plants you have .For my orchids, which need good=fast drainage and air circulation , I use small gravel, porous rock ( lava stone ,very similar to tufa but cheaper ) , chunks of bark, charcoal and maybe a pinch of potting soil . For bromeliads and cactus , I use mostly sand and enough rock and gravel to physically support them. For large house plants ( dracaena , 6 ft tall) , I put some pieces of cast iron in the bottom of the pot for weight and drainage , then fill with potting soil plus gravel. For "gravel" ,I use garnet sand blast material , I buy 50# bags because I also use it in aquariums.

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Typical ingredients depend on the plant and soil needs. Little water holding requries good drainage. That's done with Sands or lava rocks, perlite.

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Thanks everyone for their answers and suggestions.

What I've decided to do is to use sifted compost (regular vegetal compost, not vermicompost/worm castings).

I'm using only the coarse part of the compost (the one that stays on the sieve).

This guy made a very interesting video on water retention for different materials (both organic and inorganic).

Video link

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Even though he didn't sift it in the video, you can see that the compost drains really well, and as a bonus, will also provide nutrients over time.

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